Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$231.29	5.639%	$244.3324	$244.33	$244.35	$244.30
Purchase #2	$49.69	4.735%	$52.0428	$52.04	$52.05	$52.00
Purchase #3	$88.64	12.261%	$99.5082	$99.51	$99.50	$99.50
Purchase #4	$204.27	8.772%	$222.1886	$222.19	$222.20	$222.20
Purchase #5	$85.45	3.493%	$88.4348	$88.43	$88.45	$88.40
Purchase #6	$18.34	3.264%	$18.9386	$18.94	$18.95	$18.90
Purchase #7	$223.98	6.294%	$238.0773	$238.08	$238.10	$238.10
7 purchase totals =	$901.66		$963.5227	$963.52	$963.60	$963.40